/*
 ------------------------------------------------------------------------------
 RSA Data Security, Inc., MD4 Message-Digest Algorithm
 Copyright (C) 1990-2, RSA Data Security, Inc. All rights reserved.

 License to copy and use this software is granted provided that it is
 identified as the RSA Data Security, Inc. MD4 Message-Digest Algorithm in all
 material mentioning or referencing this software or this function.

 License is also granted to make and use derivative works provided that such
 works are identified as derived from the RSA Data Security, Inc. MD4
 Message-Digest Algorithm in all material mentioning or referencing the derived
 work. RSA Data Security, Inc. makes no representations concerning either the
 merchantability of this software or the suitability of this software for any
 particular purpose. It is provided as is without express or implied warranty
 of any kind.

 These notices must be retained in any copies of any part of this documentation
 and/or software.
 ------------------------------------------------------------------------------
*/


#include "gamelib.h"


typedef unsigned char *			POINTER;
typedef unsigned short int		UINT2;
typedef unsigned long int		UINT4;

#define S11						3
#define S12						7
#define S13						11
#define S14						19
#define S21						3
#define S22						5
#define S23						9
#define S24						13
#define S31						3
#define S32						9
#define S33						11
#define S34						15

// F, G and H are basic MD4 functions
#define F(x, y, z)				(((x) & (y)) | ((~x) & (z)))
#define G(x, y, z)				(((x) & (y)) | ((x) & (z)) | ((y) & (z)))
#define H(x, y, z)				((x) ^ (y) ^ (z))

// ROTATE_LEFT rotates x left n bits
#define ROTATE_LEFT(x, n)		(((x) << (n)) | ((x) >> (32-(n))))

// FF, GG and HH are transformations for rounds 1, 2 and 3.
// Rotation is separate from addition to prevent recomputation.
#define FF(a, b, c, d, x, s)	{(a) += F((b), (c), (d)) + (x); (a) = ROTATE_LEFT((a), (s)); }
#define GG(a, b, c, d, x, s)	{(a) += G((b), (c), (d)) + (x) + (UINT4)0x5A827999; (a) = ROTATE_LEFT((a), (s)); }
#define HH(a, b, c, d, x, s)	{(a) += H((b), (c), (d)) + (x) + (UINT4)0x6ED9EBA1; (a) = ROTATE_LEFT((a), (s)); }

typedef struct {
	UINT4		state[4];			// State (ABCD)
	UINT4		count[2];			// Number of bits, modulo 2^64 (LSB first)
	byte		buffer[64];			// Input buffer
} MD4_CTX;

static byte		PADDING[64] = {
	0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};


/*
 ==================
 MD4_Encode

 Encodes input into output.
 Assumes len is a multiple of 4.
 ==================
*/
static void MD4_Encode (byte *output, UINT4 *input, uint len){

	uint	i, j;

	for (i = 0, j = 0; j < len; i++, j += 4){
 		output[j+0] = (byte)(input[i] & 0xff);
 		output[j+1] = (byte)((input[i] >> 8) & 0xff);
 		output[j+2] = (byte)((input[i] >> 16) & 0xff);
 		output[j+3] = (byte)((input[i] >> 24) & 0xff);
	}
}

/*
 ==================
 MD4_Decode

 Decodes input into output.
 Assumes len is multiple of 4.
 ==================
*/
static void MD4_Decode (UINT4 *output, byte *input, uint len){

	uint	i, j;

	for (i = 0, j = 0; j < len; i++, j += 4)
 		output[i] = ((UINT4)input[j]) | (((UINT4)input[j+1]) << 8) | (((UINT4)input[j+2]) << 16) | (((UINT4)input[j+3]) << 24);
}

/*
 ==================
 MD4_Transform

 MD4 basic transformation.
 Transforms state based on block.
 ==================
*/
static void MD4_Transform (UINT4 state[4], byte block[64]){

	UINT4	a = state[0], b = state[1], c = state[2], d = state[3], x[16];

	MD4_Decode(x, block, 64);

	// Round 1
	FF(a, b, c, d, x[ 0], S11);				// 1
	FF(d, a, b, c, x[ 1], S12); 			// 2
	FF(c, d, a, b, x[ 2], S13); 			// 3
	FF(b, c, d, a, x[ 3], S14); 			// 4
	FF(a, b, c, d, x[ 4], S11); 			// 5
	FF(d, a, b, c, x[ 5], S12); 			// 6
	FF(c, d, a, b, x[ 6], S13); 			// 7
	FF(b, c, d, a, x[ 7], S14); 			// 8
	FF(a, b, c, d, x[ 8], S11); 			// 9
	FF(d, a, b, c, x[ 9], S12); 			// 10
	FF(c, d, a, b, x[10], S13); 			// 11
	FF(b, c, d, a, x[11], S14); 			// 12
	FF(a, b, c, d, x[12], S11); 			// 13
	FF(d, a, b, c, x[13], S12); 			// 14
	FF(c, d, a, b, x[14], S13); 			// 15
	FF(b, c, d, a, x[15], S14); 			// 16

	// Round 2
	GG(a, b, c, d, x[ 0], S21); 			// 17
	GG(d, a, b, c, x[ 4], S22); 			// 18
	GG(c, d, a, b, x[ 8], S23); 			// 19
	GG(b, c, d, a, x[12], S24); 			// 20
	GG(a, b, c, d, x[ 1], S21); 			// 21
	GG(d, a, b, c, x[ 5], S22); 			// 22
	GG(c, d, a, b, x[ 9], S23); 			// 23
	GG(b, c, d, a, x[13], S24); 			// 24
	GG(a, b, c, d, x[ 2], S21); 			// 25
	GG(d, a, b, c, x[ 6], S22); 			// 26
	GG(c, d, a, b, x[10], S23); 			// 27
	GG(b, c, d, a, x[14], S24); 			// 28
	GG(a, b, c, d, x[ 3], S21); 			// 29
	GG(d, a, b, c, x[ 7], S22); 			// 30
	GG(c, d, a, b, x[11], S23); 			// 31
	GG(b, c, d, a, x[15], S24); 			// 32

	// Round 3
	HH(a, b, c, d, x[ 0], S31);				// 33
	HH(d, a, b, c, x[ 8], S32); 			// 34
	HH(c, d, a, b, x[ 4], S33); 			// 35
	HH(b, c, d, a, x[12], S34); 			// 36
	HH(a, b, c, d, x[ 2], S31); 			// 37
	HH(d, a, b, c, x[10], S32); 			// 38
	HH(c, d, a, b, x[ 6], S33); 			// 39
	HH(b, c, d, a, x[14], S34); 			// 40
	HH(a, b, c, d, x[ 1], S31); 			// 41
	HH(d, a, b, c, x[ 9], S32); 			// 42
	HH(c, d, a, b, x[ 5], S33); 			// 43
	HH(b, c, d, a, x[13], S34); 			// 44
	HH(a, b, c, d, x[ 3], S31); 			// 45
	HH(d, a, b, c, x[11], S32); 			// 46
	HH(c, d, a, b, x[ 7], S33); 			// 47
	HH(b, c, d, a, x[15], S34);				// 48

	state[0] += a;
	state[1] += b;
	state[2] += c;
	state[3] += d;

	// Zeroize sensitive information
	memset((POINTER)x, 0, sizeof(x));
}

/*
 ==================
 MD4_Init

 MD4 initialization.
 Begins an MD4 operation, writing a new context.
 ==================
*/
static void MD4_Init (MD4_CTX *context){

	context->count[0] = context->count[1] = 0;

	// Load magic initialization constants
	context->state[0] = 0x67452301;
	context->state[1] = 0xEFCDAB89;
	context->state[2] = 0x98BADCFE;
	context->state[3] = 0x10325476;
}

/*
 ==================
 MD4_Update

 MD4 block update operation.
 Continues an MD4 message-digest operation, processing another message block,
 and updating the context.
 ==================
*/
static void MD4_Update (MD4_CTX *context, byte *input, uint inputLen){

	uint	i, index, partLen;

	// Compute number of bytes mod 64
	index = (uint)((context->count[0] >> 3) & 0x3F);

	// Update number of bits
	if ((context->count[0] += ((UINT4)inputLen << 3)) < ((UINT4)inputLen << 3))
		context->count[1]++;

	context->count[1] += ((UINT4)inputLen >> 29);

	partLen = 64 - index;

	// Transform as many times as possible
	if (inputLen >= partLen){
 		memcpy((POINTER)&context->buffer[index], (POINTER)input, partLen);
 		MD4_Transform(context->state, context->buffer);

 		for (i = partLen; i + 63 < inputLen; i += 64)
 			MD4_Transform(context->state, &input[i]);

 		index = 0;
	}
	else
 		i = 0;

	// Buffer remaining input
	memcpy((POINTER)&context->buffer[index], (POINTER)&input[i], inputLen-i);
}

/*
 ==================
 MD4_Final

 MD4 finalization.
 Ends an MD4 message-digest operation, writing the message digest and zeroizng
 the context.
 ==================
*/
static void MD4_Final (MD4_CTX *context, byte digest[16]){

	byte	bits[8];
	uint	index, padLen;

	// Save number of bits
	MD4_Encode(bits, context->count, 8);

	// Pad out to 56 mod 64
	index = (uint)((context->count[0] >> 3) & 0x3F);
	padLen = (index < 56) ? (56 - index) : (120 - index);
	MD4_Update(context, PADDING, padLen);

	// Append length (before padding)
	MD4_Update(context, bits, 8);
	
	// Store state in digest
	MD4_Encode(digest, context->state, 16);

	// Zeroize sensitive information
	memset((POINTER)context, 0, sizeof(*context));
}


// ============================================================================


/*
 ==================
 MD4_BlockChecksum
 ==================
*/
ulong MD4_BlockChecksum (const void *data, int length){

	MD4_CTX	ctx;
	ulong	digest[4];
	ulong	val;

	MD4_Init(&ctx);
	MD4_Update(&ctx, (byte *)data, length);
	MD4_Final(&ctx, (byte *)digest);
	
	val = digest[0] ^ digest[1] ^ digest[2] ^ digest[3];

	return val;
}
